JPH06263849A - Production of polyester - Google Patents

Abstract

PURPOSE:To improve the heat stability and wet heat resistance of polybutylene naphthalenedicarboxylate. CONSTITUTION:Naphthalenedicarboxylic acid and tetramethylene glycol are subjected to melt polycondensation under conditions such that 0.5-10mol% glycol ester of oxalic acid of the formula [wherein R is butylene; and (n) is an integer of 4 or lower] is added when the intrinsic viscosity reaches 0.5 or higher, then the polycondensation is further continued if necessary, and thus the intrinsic viscosity is increased to a specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a polybutylene naphthalene dicarboxylate polymer (hereinafter sometimes abbreviated as polybutylene naphthalate or PBN) which is excellent in thermal stability and heat resistance. .

[0002]

2. Description of the Related Art Conventional polyesters containing tetramethylene glycol as a main glycol component, for example, polybutylene terephthalate (hereinafter abbreviated as PBT) PBN polymers are polyesters containing ethylene glycol as a main glycol component, for example, Compared with polyethylene terephthalate (hereinafter abbreviated as PET) and polyethylene naphthalate (hereinafter abbreviated as PEN), it has a higher crystallization rate and is excellent in molding recycling and appearance of molded products, so various molded products, especially engineering plastics. It is used in a wide range of fields as a material.
However, in recent years, electronic parts and electrical parts such as connectors, automobile parts, and other molded parts have become smaller and thinner, and the environment in which they are used is becoming more and more severe, requiring products with excellent heat resistance and mechanical properties. It has come to be done. In particular, since polyesters have an ester bond, they are generally susceptible to hydrolysis, and improvement of dry heat resistance and wet heat resistance is an important issue.

As a method for improving these dry heat resistance and wet heat resistance, it is already known that reducing the concentration of terminal carboxyl groups of a polymer is effective, and the present invention provides a method for producing a polyester having a low terminal carboxyl group concentration. To do.

In the prior art, in the case of PET, there is known a technique for reducing the concentration of carboxyl groups by adding ethylene carbonate, diphenyl terephthalate, epoxy compound, bisoxazoline, polyoxalate compound and the like. Further, in the case of reducing the carboxyl group in the case of PBT, a technique by adding an alkaline metal compound is known. Although the addition of an alkali metal compound is a method which is sufficiently satisfactory for achieving the above-mentioned object, when an alkali metal compound is added to the melt polymerization of PBT, the polymerization reaction rate remarkably decreases and the production efficiency deteriorates, which is not preferable. On the other hand, for bisoxazoline compounds, PET
Although the effect of low COOH group concentration is very excellent in PBT and PBT, it is not practical because gas is generated due to decomposition of the agent which is considered to be due to unreacted during dry heat deterioration and the polymer is significantly discolored. The addition of a polyoxalate compound to PET or PBT and its effect are described in JP-B-48-35953 and JP-A-4-311720, but PBN is not described at all.

By the way, when a polyoxalate compound is used for PET, the compound represented by the general formula (II)

[0006]

[Chemical 2]

It has been assumed in the literature that if the number of carbon atoms of the alkylene group of R ₁ is 2 or more, there will be no difference in effect. However, in the polyoxalate compound, due to the alkylene group,
It was not known at all that the properties of the polymer, in other words, the addition effect of the polyoxalate compound was different, but the present inventors have obtained new findings in this respect.

The mechanism for lowering the concentration of the carboxyl group is due to the reaction between the terminal carboxyl group of the polyester and the polyozate, and since the alkylene group of R ₁ is incorporated into the polyester main chain, the alkylene group of the main skeleton of the polyester is And the carbon number is different, the melting point is lowered and the crystallinity is lowered.

On the other hand, Japanese Patent Laid-Open No. 4-3117 relating to PBT
In No. 20, the alkylene group of R ₁ is restricted,
It has the effect of reducing the concentration of terminal carboxyl groups without lowering the melting point and the crystallinity, and to some extent, the effect of improving heat resistance and moist heat resistance is recognized. Most recently, however, the required property level is extremely high, and a material having excellent heat resistance and moist heat resistance is required.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have used PBN as a polyester, and added a specific (poly) ester of oxalic acid or glycol ester of oxalic acid at a certain polymerization stage. By doing so, the polymerization reactivity, the melting point and the crystallinity are not lowered, the concentration of the carboxyl group can be reduced, and the heat resistance and the moist heat resistance which cannot be achieved by the conventional PEN or the improved PBT are very excellent. They found what was obtained and reached the present invention.

That is, according to the present invention, when a polyester having naphthalene dicarboxylic acid as a main acid component and glycol having a carbon number of 4 as a main glycol component is produced by melt polymerization, the polyester intrinsic viscosity number in the polymerization process of the polyester production is After reaching 0.5, a low polymerization degree oxalic acid-based oligomer having a degree of polymerization of 4 or less, which contains a glycol ester of oxalic acid represented by the formula (I) and / or oxalic acid as a main acid component, is added to the reaction system at 0 or less. The PBN production method comprises adding 5 to 10 mol% in an amount and then performing a polymerization reaction.

In the present invention, PBN is a polyester containing naphthalenedicarboxylic acid as a main acid component and glycol having an oxygen number of 4 as a main glycol component.
The term "mainly" as used herein means that it accounts for 80 mol% or more of all acid components or all glycol components, and includes those obtained by copolymerizing 20 mol% or less of a third component. As the third component, 10 mol% or less is particularly preferable. Further, as the copolymerizable third component, an aromatic dicarboxylic acid other than naphthalene dicarboxylic acid, for example, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylketonedicarboxylic acid, sodium sulfoisophthalic acid. Acids, dibromoterephthalic acid and the like; alicyclic dicarboxylic acids such as oxahydroterephthalic acid, decalin dicarboxylic acid and the like; aliphatic dicarboxylic acids such as malonic acid and succinic acid,
Adipic acid, etc .; aliphatic diols other than butanediol,
For example, ethylene glycol, trimethylene glycol,
Neopentyl glycol, diethylene glycol, etc .; aromatic dihydroxy compounds such as bisphenol A
[2,2′-bis (4-hydroxyphenyl) propane], bisphenol S, tetrabromobisphenol A, bishydroxyethoxybisphenol A, etc .; aliphatic oxycarboxylic acids such as asiatic acid, quinobaic acid, etc .; aromatic oxycarboxylic acids Examples thereof include acids such as P-hydroxybenzoic acid, P-hydroxyethoxybenzoic acid, mandelic acid, and tetrolactic acid. These third components may be used alone or in combination of two or more. Further, the copolyester is a polyfunctional compound having a valence of 3 or more, for example, glycerin, trimethylolpropane, pentaerythrite, trimellitic acid, trimesic acid, within a range in which the polymer can be regarded as substantially linear.
A small amount of pyromellitic acid, tricarbaline acid or the like may be copolymerized, or a monofunctional compound such as O-benzoylbenzoic acid or naphthoic acid may be bonded, or a monofunctional compound such as O-benzoyl. Benzoic acid, naphthoic acid, etc. may be bonded.

PBN can be produced by a usual melt polymerization method.
For example, transesterification reaction between dimethylnaphthalate and 1,4-butanediol is carried out, or naphthalate dicarboxylic acid and 1,4-butanediol are directly esterified to give substantially bis (β-hydroxy). Butyl) naphthalene dicarboxylate or a low polymer thereof can be formed, and this can be produced by polycondensation under reduced pressure of 260 ° C. or higher.

According to the present invention, a glycol ester of oxalic acid represented by the following formula (I) and / or an oxalic acid oligomer is added during the polycondensation reaction of PBN. Use here

[0015]

[Chemical 3]

[Wherein R represents a butylene group having 4 carbon atoms and n represents an integer of 4 or less]. ] The low polymer of oxalic acid glycol ester and / or oxalic acid type polyester is an ester of 1,4-butanediol having 4 carbon atoms as a glycol component in order not to lower the melting point and the crystallinity of PBN described above. It is essential to make it a compound.

The addition time of the oxalic acid glycol ester or oxalic acid ester oligomer is the same as the above PB.
It is after the stage where the intrinsic viscosity of N reaches at least 0.5. In particular, it is preferable to add it because the intrinsic viscosity becomes 0.7 or more. If added before the intrinsic viscosity is less than 0.5, the intrinsic viscosity of PBN at the time of addition becomes very low and the subsequent polycondensation time becomes long, and the concentration of carboxyl group of PBN increases again. As a result, the object of the present invention cannot be achieved. The amount of glycol ester added is preferably 0.5 to 10.0 mol%, and particularly preferably 1.0 to 7.0 mol%.

If the amount added is less than this lower limit, PBN having a sufficiently low carboxyl group concentration cannot be obtained. On the contrary, if the amount added is too large, the intrinsic viscosity after addition is large, and significant foaming occurs, which causes a reaction process. And the subsequent polycondensation reaction takes a long time, resulting in a significant increase in the concentration of the carboxyl group of PBN, resulting in poor heat resistance.

When producing the PBN, ordinary catalysts, stabilizers and various additives may be added as required.

The PBN obtained by the present invention can be used as a mechanical structural material or an automobile part.

[0021]

The function and effect of the present invention are as follows.
Rather, it is possible to manufacture PBN having a low carboxyl group concentration without lowering the melting point and the crystallinity, and to obtain PBN with improved thermal stability and moist heat resistance compared to conventional PBN and improved PBT. be able to.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples. In the examples, "part" indicates part by weight, and the characteristic value is
The procedure was as follows. -Intrinsic viscosity: [η] Phenol / tetrachloroethane = 3/2 solvent,
It was calculated from the solution viscosity measured at 35 ° C. -Carboxyl group concentration: COOH (equivalent / 10 ⁶ g) A-CONIX method (Makromol, chem, 26 226 (195
8)). -Evaluation of dry heat deterioration property: The polymer sample was processed at 180 ° C for 7 days in the air using a gear deterioration tester, and the [η] reduction degree at that time was obtained.・ Evaluation of wet heat deterioration: dip a polymer sample in pure water,
The boiling water treatment was performed, and the degree of decrease in [η] at that time was obtained. Melting point and crystallinity: 1090B type DS manufactured by Dupont
Using C, sample 10mg at 20 ℃ / min at 300 ℃
The temperature was raised to 1, held for 2 minutes and then lowered at 10 ° C./min to measure the melting point peak temperature (Tm) and the high temperature crystallization peak temperature (Tcd).

[Synthesis Example 1] 1,4-butanediol 4.
Titanium tetraoxide (0.02 part) was dissolved in 9 parts, diethyl oxalate (4.0 parts) was added, and the mixture was heated to 160 ° C. to distill off ethyl alcohol produced as a result of the transesterification reaction. After that, the pressure was gradually reduced under an N ₂ atmosphere, and the mixture was heated and reacted under 20 mmHg for about 10 minutes. The average degree of polymerization of the oxalic acid butylene ester polymer obtained at this time was 1.6.

[Synthesis Example 2] 0.03 part of manganese acetate was dissolved in 3.4 parts of ethylene glycol, 4.0 parts of diethyl oxalate was added, and the mixture was heated to 160 ° C. to produce ethyl alcohol as a result of transesterification reaction. Was distilled. Then, 0.02 part of phosphorous acid was added, the pressure was gradually reduced under N ₂ atmosphere, and the mixture was heated and reacted under 20 mmHg for about 10 minutes. The average degree of polymerization of the oxalic acid ethylene ester polymer obtained at this time was 1.4.

[0025]

Example 1 2.6-Dimethylnaphthalate 35.0
Part, 1,4-butanediol 20.7 parts, tetra-n-
Butyl titanate 0.008 parts and Irganox 10
760.040 parts were charged into a transesterification reaction tank, and 2
A transesterification reaction (abbreviated as EI reaction) was carried out at 10 ° C. for 180 minutes, and methanol distilled during the reaction was distilled out of the reaction system. The amount of methanol distilled at the end of the reaction is 1
It was 0.4 parts. After completion of the EI reaction, the reaction solution was transferred to a polycondensation tank for a polycondensation reaction (abbreviated as PN reaction), and the reaction temperature was adjusted to 210 at a reaction temperature of 35 minutes while gradually increasing the vacuum degree.
It was made to reach from 260C to 260C. Hold this temperature,
The degree of vacuum was kept at 0.3 mmHg and the PN reaction was carried out for 170 minutes. Here, the reaction system was returned to normal pressure using N ₂ . The intrinsic viscosity of the obtained polymer was 0.60. Here, the reaction system was returned to normal pressure with N ₂ gas, 0.56 parts of butyl oxalate ester polymer of Synthesis Example 1 (2.0 mol% based on all acid components constituting PBN) was added, and then gradually added. Then, the pressure was returned to reduced pressure and the PN reaction was continued under a reduced pressure of 0.3 mmHg until the desired intrinsic viscosity was reached (20 minutes). The polymer obtained had an intrinsic viscosity of 0.78 and a carboxyl group concentration of 12 equivalents / 10 ⁶ g.

[0026]

Examples 2 to 3 and Comparative Examples 2 to 4 As in Example 1, except that the addition timing and amount of the oxalic acid butyl ester polymer (Synthesis Example 1) were changed as shown in Table 1. went.

[0027]

[Comparative Example 1] P was added without adding an oxalate polymer.
During the N reaction, a normal reaction is performed without returning to normal pressure of N ₂ .
Example 1 was repeated except that the desired intrinsic viscosity was obtained.

[0028]

Comparative Example 5 Oxalic acid butyl ester polymer was changed to 0.69 parts by weight of oxalic acid ethylene ester polymer (Synthesis Example 2) (3.0 mol% based on all acid components constituting PBN). Except for this, the same procedure as in Example 1 was performed.

[0029]

Comparative Example 6 35.0 parts of dimethyl terephthalate 1,
4-Butanediol 22.9 parts, tetra-n-butyl titanate 0.026 parts and Irganox 1076
Then, 0.040 parts was charged into a transesterification reaction tank, and 170
A transesterification reaction (abbreviated as EI reaction) was carried out at 180 ° C. for 180 minutes, and methanol distilled during the reaction was distilled out of the reaction system. The amount of methanol distilled at the end of the reaction was 10.4.
It was a department. After completion of the EI reaction, the reaction solution is subjected to a polycondensation reaction (P
It was transferred to a polycondensation tank for N reaction), and the reaction temperature was raised from 170 ° C to 245 ° C over 35 minutes while gradually increasing the degree of vacuum. While maintaining this temperature, the degree of vacuum was maintained at 0.3 mmHg, and the PN reaction was performed for 110 minutes. Here, the reaction system was returned to normal pressure using N ₂ . The intrinsic viscosity of the obtained polymer was 0.69. Here, the reaction system was returned to normal pressure with N ₂ gas, 0.70 parts of butyl oxalate polymer of Synthesis Example 1 (2.0 mol% based on all acid components constituting PBN) was added, and then gradually added. Then, the pressure was returned to reduced pressure and the PN reaction was continued under a reduced pressure of 0.3 mmHg until the desired intrinsic viscosity was reached (20 minutes). The polymer obtained had an intrinsic viscosity of 0.88 and a carboxyl group concentration of 13 equivalents / 10 ⁶ g.

The quality, melting point, dry heat deterioration evaluation and wet heat deterioration evaluation results of the PBN and PBT obtained above are shown in Table 1.

As is clear from Table 1, when a butyl oxalate polymer was added at a specific addition amount above a certain intrinsic viscosity, the melt polymerization rate was also improved and the obtained DBN was obtained.
It can be seen that the carboxyl group concentration of is low. Comparative Example 5
It was found that when the oxalic acid polyester polymer is other than a C4 butylene group, the melting point of PBN is lowered and the crystallinity is inferior. It was found from Comparative Example 6 that it was superior to PBT having a reduced carboxyl group concentration.

[0032]

[Table 1]

Claims (1)

[Claims] 1. When melt-polymerizing a polymer containing naphthalenedicarboxylic acid as a main acid component and tetramethylene glycol as a main glycol component, after the intrinsic viscosity of the polymer reaches 0.5 or more, the following formula (I) [Chemical 1] [However, R in the formula represents a butylene group, and n represents an integer of 4 or less. ] The low-degree oligomer having an oxalic acid glycol ester and / or oxalic acid as an acid component represented by
5 to 10.0 mol% (provided that the oxalic acid ester is n =
In the case of one or more, the repeating unit thereof is regarded as 1 mol), and the polymerization reaction is continuously continued to reach a predetermined intrinsic viscosity.